1. Field of the Invention
The present invention generally relates to manually powered- fastening devices and specifically to impact driven staple guns and tacking machines.
2. Description of the Related Art
The fastening tool of the invention may use an operating principle similar to that disclosed in several U.S. patents, including U.S. Pat. No. 5,407,118 to Marks. In Marks, an operating handle is hinged at a rear end of the tool housing while a staple is ejected from the bottom front end. A staple feeding track slides rearward from the bottom of the tool body to expose a staple holding chamber. A releasable latch retains the track from sliding rearward.
U.S. Pat. No. 2,326,540 issued to Krantz discloses a staple gun in which a hand lever is pivoted at the back and an actuating lever is pivoted above the hand grip opening with a lifting end engaging the rear portion of a large plunger lifting assembly.
U.S. Pat. No. 2,769,174 issued to Libert discloses a staple gun in which a hand lever is pivoted at the back and an actuating lever is pivoted in front of the hand grip opening with a lifting end still further forward of the hand grip opening.
UK Patent Spec. No. 807 937 issued to Seimsen and Post discloses a staple gun in which a hand lever is pivoted at the rear end and an actuating wheel is located in front of the hand grip opening with lifting ends engaging a plunger in front of the wheel.
U.S. Pat. No. 3,862,712 issued to LaPointe et al. discloses a staple gun with a staple feeding track that slides rearward to expose a staple loading chamber. A releasable latch assembly retains the track in position.
U.S. Pat. No. 4,119,258 issued to Ewig Jr. discloses a staple gun with a body and hand lever constructed substantially of plastic material. U.S. Pat. No. 4,150,774 issued to Wright discloses a staple gun with a staple feeding track including a rearwardly cantilevered flexible latch.
European Patent Published Specification No. 0 281 541 B1, filed by B. Westerland discloses a staple gun with a hand lever pivoted near the front, a flat plunger, and a spring elongated rearward from the front.
U.K. Patent Application No. 2 032 327 A (Barrlendos) discloses a staple gun with a hand lever pivoted near the front, a flat plunger, and a coiled wire torsion spring elongated rearward from the front. The plunger center links to the spring and the plunger top links to the lever. Barrlendos shows a common design for a simplified staple gun. The tool is gripped from behind the lever pivot location and the hand tool occupies the rear portion of the tool body. Substantially front to back forces are generated upon the plunger as a result of angles at which the lever and spring engage the plunger and the large separation between the lever and the spring at the plunger.
U.K. Patent Application No. 2 229 129 A (Chang) discloses a desktop stapler with an actuating lever pivoted near the front and a hand lever pivoted at the rear. An elongated torsion spring is energized when the device is in the rest state. Pressing the hand lever immediately releases the plunger and spring. Chang does not teach any means for raising the plunger and re-energizing the spring.
None of the foregoing teach the making of a staple gun which may be gripped and operated at the front end. For example, both Libert and Krantz show a large vertical spring and plunger assembly that occupies a substantial portion of the front end of the tool. Chang discloses a desktop stapler with a permanently attached base and a solid sided housing. The method of operation differs from the present invention in that the spring is energized when the device is in an initial state. There is no mechanism to complete an operating cycle; in particular, there is teaching with respect to a structure to raise the plunger.